Antibiotic residues in foods are a major food safety concern. Health issues include bacterial resistance to drugs and allergic reactions. To avoid the impact of such health issues, food is tested worldwide for antibiotics and other contaminants. One type of test method uses what is commonly known as a lateral flow test strip.
Lateral-flow test strips for detecting one or more analytes in a fluid sample may include a capture agent immobilized within a region of the test sometimes referred to as a detection zone. Detection zones can include test zones and control zones. A typical capture agent has binding affinity for a substance that may be in the mobile phase of the test strip. Lateral-flow tests in which the binding of a substance from a mobile phase to a capture agent generates a visible signal, that can be interpreted visually or using a reader, such as a spectrophotomer, are well known in the art. Examples of such devices are described in U.S. Pat. No. 5,985,675, issued Nov. 16, 1999; and U.S. Pat. No. 6,319,466, issued Nov. 20, 2001, and U.S. patent application Ser. No. 10/289,089, filed Nov. 6, 2002 (based on U.S. Provisional Application 60/332,877, filed Nov. 6, 2001) all of which are incorporated herein by reference.
Lateral-flow tests are widely used in the food products industry. One application is in testing dairy products. However, other fluids often contain characteristics that limit, or even prohibit, efficient use of traditional lateral-flow tests. For example, citrus juices and oils may not be compatible with conventional lateral-flow tests because of their low pH. Yet, these, and other low pH fluids, are subject to regulation by the United States Food and Drug Administration (FDA). For example, citrus juices are commonly treated with antibiotics to prevent citrus cankers and other fungal infections. While the FDA has approved certain antibiotics, such as oxytetracycline and streptomycin, the FDA has prohibited others, such as penicillin, and requires that citrus juices and oils be tested for unsafe levels of certain beta-lactam antibiotics. It is desirable, therefore, to provide juice-testing personnel with a user-friendly test that can be analyzed with or without a reader and can detect multiple beta-lactams, such as penicillin, when present at or above a threshold level.
Therefore, Applicants desire detection of residues in a low pH sample without the drawbacks presented by the traditional systems and methods.